Developing Apparatus

The present disclosure relates to a developing apparatus that develops an electrostatic latent image formed on an image bearing member with a developer.

As a developing apparatus, a configuration including a peeling roller for peeling and collecting a developer from a developing roller that develops an electrostatic latent image formed on an image bearing member with a developer has been proposed (Japanese Patent Application Laid-Open Publication No. 2018-124338). The developing roller includes a developing sleeve that rotates, and a developing magnet disposed non-rotatably inside the developing sleeve, wherein the developer is borne on a surface of the developing sleeve by magnetic force of the developing magnet. Similarly, the peeling roller includes a peeling sleeve that rotates, and a peeling magnet disposed non-rotatably inside the peeling sleeve, wherein the developer is borne on a surface of the peeling sleeve by magnetic force of the peeling magnet. The developer having been carried and fed by the developing sleeve and used to develop the electrostatic latent image on the image bearing member, i.e., used developer, is borne on the surface of the peeling sleeve, by which the developer on the developing roller is collected by the peeling roller. Then, by the rotation of the peeling sleeve, the developer borne on the peeling sleeve is conveyed to a peeling position, and the developer is peeled off from the peeling sleeve.

According to the configuration disclosed in Japanese Patent Application Laid-Open Publication No. 2018-124338, the peeling sleeve is rotated such that the surface of the peeling sleeve moves in an opposite direction as the surface of the developing sleeve at an opposing portion opposing the developing sleeve. In this state, during a process of delivering the developer from the developing sleeve to the peeling sleeve, scattering of toner caused by collapse of napping of the developer between magnetic poles during feeding of the developer being delivered from the developing sleeve to the peeling sleeve and fed to the peeling position may occur, and scattering of detached toner during peeling may also occur.

Along with the recent increase in speed of the image forming apparatus, such scattering of toner from the peeling roller has become an issue, and many developing apparatuses are provided with a duct for sucking the toner that has been scattered inside the developing apparatus. However, in such a configuration, a carrier that has been scattered together with the scattered toner from the peeling roller is collected by the duct, such that the duct may be clogged by the carrier. When the duct is clogged by the carrier, the ability of the duct to suck the scattered toner is deteriorated, such that toner scattering may not be suppressed sufficiently.

One aspect of the present disclosure is to suppress the collecting of carrier by the duct.

According to one aspect of the present disclosure, a developing apparatus includes a developing container including a first chamber configured to contain a developer including a toner and a carrier, and a second chamber partitioned from the first chamber by a partition wall, a first rotatable developing member to which the developer is supplied, the first rotatable developing member being configured to carry and feed the developer to a developing position where an electrostatic latent image formed on an image bearing member is developed, a first magnet provided non-rotatably and stationarily inside the first rotatable developing member, the first magnet having a first magnetic pole provided to face the image bearing member at the developing position, a second magnetic pole provided downstream of the first magnetic pole in a rotational direction of the first rotatable developing member, and a third magnetic pole provided downstream of the second magnetic pole and adjacent to the second magnetic pole, with respect to the rotational direction of the first rotatable developing member, and having a same magnetic polarity as that of the second magnetic pole, a second rotatable developing member disposed to face the first rotatable developing member and configured to receive the developer delivered from the first rotatable developing member by a magnetic field generated by the first magnet, the second rotatable developing member being configured to carry and feed the developer after developing the electrostatic latent image in the second chamber to collect the developer in the second chamber, a second magnet provided non-rotatably and stationarily inside the second rotatable developing member, the second magnet having a fourth magnetic pole having a different magnetic polarity from that of the second magnetic pole, a fifth magnetic pole provided downstream of the fourth magnetic pole with respect to a rotational direction of the second rotatable developing member, a sixth magnetic pole provided downstream of the fifth magnetic pole and adjacent to the fifth magnetic pole, with respect to the rotational direction of the second rotatable developing member, and having a different magnetic polarity from that of the fifth magnetic pole, and a seventh magnetic pole provided downstream of the sixth magnetic pole and adjacent to the sixth magnetic pole, with respect to the rotational direction of the second rotatable developing member, and having a same magnetic polarity as that of the sixth magnetic pole, wherein the developer after developing the electrostatic latent image is delivered from the first rotatable developing member to the second rotatable developing member by a magnetic field generated between the second magnetic pole and the fourth magnetic pole, and, a duct including a suction port that is an inlet through which the developer scattered in the developing container is sucked, the suction port being disposed downstream, in the rotational direction of the second rotatable developing member, of a position at which the first rotatable developing member and the second rotatable developing member face each other, a first duct wall configured to extend downstream, in the rotational direction of the second rotatable developing member, of the suction port, the first duct wall disposed to face a part of the second rotatable developing member with a gap therebetween, and a second duct wall disposed to face the first duct wall and configured to form a space between the second duct wall and the first duct wall through which the developer sucked from the suction port flows, the second duct wall being positioned on an outer side than the first duct wall with respect to a rotation center of the second rotatable developing member in a direction from the rotation center of the second rotatable developing member toward a position on an outer peripheral surface of the second rotatable developing member where an absolute value of a normal component of a magnetic flux density of the sixth magnetic pole becomes maximum. The rotational direction of the second rotatable developing member is opposite from the rotational direction of the first rotatable developing member at the position at which the first rotatable developing member and the second rotatable developing member face each other. The position on the outer peripheral surface of the second rotatable developing member where the absolute value of the normal component of the magnetic flux density of the sixth magnetic pole becomes maximum is positioned downstream of an edge of the first duct wall on the suction port side with respect to the rotational direction of the second rotatable developing member.

Features of the present disclosure will become apparent from the following description of embodiments with reference to the attached drawings. The following description of embodiments is described by way of example.

1 6 FIGS.to 1 FIG. An embodiment will be described with reference to. First, a schematic configuration of an image forming apparatus of the present embodiment will be described with reference to.

100 100 100 1 FIG. An image forming apparatusis a full-color image forming apparatus, and in the present embodiment, for example, is a multi-function peripheral (MFP) having a copy function, a printer function, and a scan function. As illustrated in, the image forming apparatusincludes image forming units PY, PM, PC, and PK that perform image forming processes for toner images of four colors of yellow, magenta, cyan, and black, respectively, that are arranged in parallel. The image forming apparatusaccording to the present embodiment has a document reading apparatus connected to an image forming apparatus body, i.e., apparatus body, or a host apparatus such as a personal computer connected in a communicatable manner to the apparatus body. Therefore, according to an image information received from the host apparatus, a four-color full-color image of yellow (Y), magenta (M), cyan (C), and black (K) may be formed on a recording material, such as recording paper, plastic sheets, and cloths, using an electrophotographic system.

21 21 21 21 1 1 1 1 22 22 22 22 28 28 28 28 26 26 26 26 100 2 3 The image forming units PY, PM, PC, and PK of the respective colors include primary chargersY,M,C, andK, developing apparatusesY,M,C, andK, exposure devicesY,M,C, andK, photosensitive drumsY,M,C, andK, and cleaning devicesY,M,C, andK. The image forming apparatusincludes a transfer deviceand a fixing device. Since configurations of the image forming units PY, PM, PC, and PK of the respective colors are similar to each other, the image forming unit PY will be described below as a representative.

28 28 21 28 28 The photosensitive drumY serving as an image bearing member is a photosensitive member including a photosensitive layer made of a resin such as a polycarbonate resin containing an organic photoconductor (OPC), and is configured to rotate at a predetermined speed. According to the present embodiment, a linear velocity of the surface of the photosensitive drumY is set to 650 mm/s. The primary chargerY includes a corona discharge electrode disposed around the photosensitive drumY, and charges the surface of the photosensitive drumY with generated ions.

22 28 1 28 28 The exposure deviceY incorporates a scanning optical device, and exposes the charged photosensitive drumY based on image data to lower a potential of an exposed portion, thereby forming a charge pattern, i.e., electrostatic latent image, corresponding to the image data. The developing apparatusY transfers a developer accommodated therein to the photosensitive drumY to develop the electrostatic latent image formed on the photosensitive drumY. The developer is formed by mixing a carrier and a toner corresponding to each color, and the electrostatic latent image is visualized by the toner.

2 23 23 23 23 24 25 24 23 23 23 23 23 23 23 23 25 24 25 24 1 FIG. The transfer deviceincludes primary transfer rollersY,M,C, andK, an intermediate transfer belt, and a secondary transfer roller. The intermediate transfer beltis wound around the primary transfer rollersY,M,C, andK and a plurality of rollers, and is supported so as to be able to travel. The primary transfer rollersY,M,C, andK serving as primary transfer members correspond to respective colors of yellow (Y), magenta (M), cyan (C), and black (K) in order from the top in. The secondary transfer rolleris disposed outside the intermediate transfer belt, and is configured to allow a recording material to pass between the secondary transfer rollerand the intermediate transfer belt.

28 28 28 28 24 23 23 23 23 1 24 28 28 28 28 28 24 The toner images of the respective colors formed on the photosensitive drumsY,M,C, andK are sequentially transferred, i.e., primarily transferred, onto the intermediate transfer beltby the operation of a primary transfer bias applied to the primary transfer rollersY,M,C, andK at a primary transfer portion, i.e., primary transfer nip, Twhere the intermediate transfer beltand the photosensitive drumsY,M,C, andK abut on each other. For example, when forming a four-color full-color image, toner images are sequentially transferred, starting from the photosensitive drumY, on the intermediate transfer belt, such that a toner image in which the respective colors of yellow, magenta, cyan, and black are layered in a superimposed manner is formed.

115 111 112 2 24 2 24 25 24 25 2 3 Meanwhile, a recording material S stored in a cassetteserving as a recording material accommodating portion is conveyed via a pickup rollerand a registration rollertoward the transfer device. The recording material S is conveyed at a synchronized timing with the toner image on the intermediate transfer beltto a secondary transfer portion, i.e., nip portion, Twhere the intermediate transfer beltand the secondary transfer rollerserving as a secondary transfer member abut on each other. The toner image formed on the intermediate transfer beltis secondarily transferred onto the recording material S by the operation of a secondary transfer bias applied on the secondary transfer rollerat the secondary transfer portion T. Pressure and heat are applied at the fixing deviceto the recording material to which the toner image is transferred. As a result, the toner on the recording material is melted, and the color image is fixed to the recording material. Thereafter, the recording material S is discharged to the exterior of the apparatus.

3 113 112 114 2 3 When forming images on both sides of the recording material, the recording material S having passed through the fixing deviceis conveyed to a reverse conveyance passage, where the recording material S is reversed, and the recording material S is then conveyed to the registration rollerby a conveyance roller, and a toner image is transferred to a back surface of the recording material S in a similar manner as described above at the secondary transfer portion T. Then, the toner image is fixed to the back surface of the recording material S again at the fixing device.

28 28 28 28 26 26 26 26 28 28 28 28 24 29 Attached matter such as toner remaining on the photosensitive drumsY,M,C, andK after the primary transfer process is collected by the cleaning devicesY,M,C, andK. Thereby, the photosensitive drumsY,M,C, andK prepare for the subsequent image forming process. Further, attached matter such as toner remaining on the intermediate transfer beltafter the secondary transfer process is removed by an intermediate transfer belt cleaner.

100 Alternatively, the image forming apparatusaccording to the present embodiment may use the image forming unit of a desired single color, such as black, or some of the image forming units among the four colors to form a single color or a multi-color image.

27 27 27 27 1 1 1 1 27 27 27 27 1 1 1 1 Developer storagesY,M,C, andK are respectively provided corresponding to the developing apparatusesY,M,C, andK, and bottles accommodating developers corresponding to the respective colors of yellow, magenta, cyan, and black are replaceably loaded in the named order from the top. The developer storagesY,M,C, andK are configured to be able to convey, i.e., replenish, the developers to the developing apparatusesY,M,C, andK corresponding to the colors of the accommodated developers.

1 1 1 1 1 1 1 1 1 1 1 1 For example, a weight ratio of the toner of the developer contained in the bottle is 80 to 95%, and a weight ratio of the toner of the developer in each of the developing apparatusesY,M,C, andK is 5 to 10%. Therefore, once the toner is consumed to perform the development in the developing apparatusesY,M,C, andK, the developer containing the toner is replenished to compensate for the amount of consumption, and the weight ratio of the toner of the developer in each of the developing apparatusesY,M,C, andK is maintained constant.

1 1 1 1 1 1 1 1 1 1 36 37 38 1 2 5 FIGS.to 2 FIG. 1 FIG. 3 4 5 FIGS.,, and Next, the developing apparatusesY,M,C, andK will be described in detail with reference to. Since the configurations of the developing apparatusesY,M,C, andK are the same, the developing apparatusY will be described below as a representative.is a conceptual view illustrating the developing apparatusY illustrated in, andare conceptual views illustrating magnetic pole configurations of a first developing magnet, i.e., first magnet,, a second developing magnet, i.e., second magnet,, and a peeling magnet, i.e., third magnet,disposed in the developing apparatusY.

2 FIG. 1 30 31 32 42 43 44 70 70 As illustrated in, the developing apparatusY includes a first developing roller, a second developing roller, a peeling roller, a developer supplying screw, a developer stirring screw, and a developer collecting screw, and these members are housed in a developing container. The developing containeraccommodates a two-component developer containing a nonmagnetic toner and a magnetic carrier.

30 28 28 30 33 36 33 33 30 42 28 The first developing rolleris a developer bearing member that is rotationally driven, and is disposed at a position adjacent to the photosensitive drumY such that a rotational axis thereof is substantially parallel to a rotational axis of the photosensitive drumY. The first developing rollerincludes a first developing sleeve (a third rotatable developing member)that rotates, and a first developing magnet (a third magnet), i.e., fixed magnet,that is provided non-rotatably inside the first developing sleeveand attracts the developer to the surface of the first developing sleeveby a magnetic force. Then, the first developing rollerattracts, i.e., carries, the developer from the developer supplying screwbased on the magnetic force, and develops the electrostatic latent image formed on the rotating photosensitive drumY, i.e., on the image bearing member, with the developer.

21 21 33 34 1 21 28 22 21 Specifically, for example, a DC developing bias having a same polarity as a charging polarity of the primary chargerY, or a developing bias in which a DC voltage having a same polarity as the charging polarity of the primary chargerY is superposed to AC voltage, is applied to the first developing sleeveand a second developing sleevedescribed later of the developing apparatusY. As a result, reversal development is performed in which a toner charged to the same polarity as the charging polarity of the primary chargerY is adhered to the electrostatic latent image formed on the photosensitive drumY by the exposure deviceY. In the present embodiment, a configuration is adopted in which a reversal development is performed where the charging polarity of the primary chargerY and the DC voltage of the developing bias are set to negative and a toner charged negatively is attached to the electrostatic latent image.

33 39 33 28 33 28 33 28 2 FIG. The first developing sleeveis a nonmagnetic cylindrical member having an outer diameter of 25 mm (radius r1=12.5 mm), and is rotationally driven about a rotation shaft. A rotational direction of the first developing sleeveis a clockwise direction as indicated by an arrow in, and is a direction opposite to a rotational direction of the photosensitive drumY in the present embodiment. Therefore, the first developing sleeveand the photosensitive drumY rotate in the same direction, i.e., forward direction, at positions facing each other. That is, the first developing sleeveis rotated such that the surface facing the photosensitive drumY is moved from down to up in a vertical direction.

33 28 33 28 28 30 31 28 In the present embodiment, the linear velocity of the surface of the first developing sleeveis set to be 1.0 times (=650 mm/s) the linear velocity of the surface of the photosensitive drumY. Setting the ratio of linear velocity of the surface of the first developing sleevewith respect to the linear velocity of the surface of the photosensitive drumY to fall within approximately 1.0 times or more and 1.2 times or less is advantageous from the viewpoint of toner deterioration. Meanwhile, the amount of toner being supplied to the photosensitive drumY may be reduced and the image developing property may be deteriorated, but since the present embodiment is equipped with two developing rollersand, the amount of toner being supplied to the photosensitive drumY may be maintained even if the ratio of linear velocity is suppressed.

36 33 101 107 33 33 36 3 FIG. The first developing magnetis disposed inside the first developing sleeve, and has a plurality of magnetic polesto, as illustrated in. A space that allows rotation of the first developing sleeveis disposed between an inner periphery of the first developing sleeveand an outer periphery of the first developing magnet.

33 28 33 28 28 33 31 33 30 31 33 36 30 37 31 34 33 34 The developer attracted to the first developing sleeveis fed toward the photosensitive drumY by a rotation operation of the first developing sleeve, thereby developing the latent image formed on the photosensitive drumY. After the latent image formed on the photosensitive drumY is developed, the developer on the first developing sleeveis fed to the vicinity of the second developing rollerby the rotation operation of the first developing sleeve. Then, in the vicinity of the closest position of the first developing rollerand the second developing roller, the developer is peeled off from the first developing sleeveby a magnetic field generated by the first developing magnetwithin the first developing rollerand the second developing magnetwithin the second developing roller, and is delivered onto the second developing sleeve. The first developing sleeveand the second developing sleeveare arranged with a gap of 3 mm therebetween at the closest portion.

31 30 28 30 30 30 31 28 28 31 30 The second developing rollerserving as a developing roller is a developer bearing member that is rotationally driven, is disposed downstream of the first developing rollerin the rotational direction of the photosensitive drumY and positioned higher than a rotation center of the first developing rollerin the vertical direction, and receives the developer delivered from the first developing rollerby the magnetic force. Similar to the first developing roller, the second developing rolleris disposed at a position adjacent to the photosensitive drumY such that a rotational axis thereof is substantially parallel to the rotational axis of the photosensitive drumY. Therefore, the rotational axes of the second developing rollerand the first developing rollerare substantially parallel to each other.

31 34 37 34 34 31 30 33 28 32 31 Such a second developing rollerincludes a second developing sleeve (a first rotatable developing member)that rotates and the second developing magnet (a first magnet), i.e., fixed magnet,that is provided non-rotatably inside the second developing sleeveand attracts the developer to the surface of the second developing sleeveby a magnetic force. Then, the second developing rollerreceives the developer delivered from the first developing roller, i.e., the first developing sleeve, based on the magnetic force, attracts, i.e., carries, the developer, and develops the electrostatic latent image formed on the rotating photosensitive drumY with the developer. The peeling rollerdescribed below is positioned on a side of the second developing roller.

34 40 34 28 34 28 34 28 34 33 34 28 2 FIG. The second developing sleeveis a nonmagnetic cylindrical member having an outer diameter of 25 mm (radius r2=12.5 mm), and is rotationally driven about a rotation shaft. A rotational direction of the second developing sleeveis a clockwise direction, as indicated by an arrow in, and is a direction opposite to the rotational direction of the photosensitive drumY in the present embodiment. Therefore, the second developing sleeveand the photosensitive drumY rotate in the same direction at positions facing each other, i.e., opposing portions. That is, the second developing sleeveis rotated such that a surface facing the photosensitive drumY moves from down to up in the vertical direction. Further, the second developing sleeveand the first developing sleeverotate in opposite directions at positions facing each other. In the present embodiment, the linear velocity of the surface of the second developing sleeveis set to be 1.2 times (=780 mm/s) the linear velocity of the surface of the photosensitive drumY.

37 34 201 207 34 34 37 The second developing magnetis disposed inside the second developing sleeveand has a plurality of fan-shaped magnetic polesto. A space that allows rotation of the second developing sleeveis disposed between an inner periphery of the second developing sleeveand an outer periphery of the second developing magnet.

34 28 34 28 28 34 32 34 31 32 34 35 32 37 31 38 32 The developer attracted to the second developing sleeveis fed toward the photosensitive drumY by a rotation operation of the second developing sleeve, thereby developing the latent image formed on the photosensitive drumY. After the latent image formed on the photosensitive drumY is developed, the developer remaining on the second developing sleeveis fed to the vicinity of the peeling rollerby the rotation operation of the second developing sleeve. Then, in the vicinity of the closest positions of the second developing rollerand the peeling roller, the developer is delivered from the second developing sleeveto a peeling sleeveof the peeling rollerby a magnetic field generated by the second developing magnetwithin the second developing rollerand the peeling magnetwithin the peeling roller.

32 28 34 31 28 31 32 31 44 31 The peeling roller, i.e., collecting roller,is disposed on a side opposite to the photosensitive drumY with respect to a rotation center of the second developing sleeve, and peels, from the second developing roller, the developer after developing the electrostatic latent image on the photosensitive drumY by the second developing roller. Specifically, the peeling rolleris a developer bearing member that is rotationally driven, and is disposed between the second developing rollerand the developer collecting screwsuch that a rotation center thereof is positioned higher than a rotation center of the second developing roller.

32 31 32 35 38 35 35 31 The peeling rolleris disposed such that a rotational axis thereof is substantially parallel to the rotational axis of the second developing roller. The peeling rollerincludes the peeling sleeve (a second rotatable developing member)that rotates and the peeling magnet (a second magnet), i.e., fixed magnet,that is provided non-rotatably inside the peeling sleeveand attracts the developer to the surface of the peeling sleeveby a magnetic force, and is configured to receive the developer delivered from the second developing rollerbased on the magnetic force.

35 41 35 34 35 34 35 34 34 2 FIG. The peeling sleeveis a nonmagnetic cylindrical member having an outer diameter of 18 mm (a radius of 9 mm), and is rotationally driven about a rotation shaft. A rotational direction of the peeling sleeveis a clockwise direction as indicated by an arrow in, and is the same direction as the rotational direction of the second developing sleevein the present embodiment. Therefore, the peeling sleeveand the second developing sleeverotate in the opposite direction at positions facing each other, i.e., opposing portions. That is, the peeling sleeveis rotated such that the surface thereof moves in an opposite direction as the surface of the second developing sleevein the opposing portion that faces the second developing sleeve.

38 35 301 305 35 35 38 The peeling magnetis disposed inside the peeling sleeveand has a plurality of magnetic polesto. A space that allows rotation of the peeling sleeveis disposed between an inner periphery of the peeling sleeveand an outer periphery of the peeling magnet.

35 35 35 38 32 44 45 45 44 The developer attracted to the peeling sleeveis fed downstream in the rotational direction by the rotation operation of the peeling sleeve, is peeled off from the peeling sleeveby the peeling magnetwithin the peeling rollerat a position close to the developer collecting screw, and falls toward a guide memberpositioned lower in the vertical direction by its own weight. Then, the developer falling onto the guide memberis guided by its own weight toward the developer collecting screw.

45 44 47 35 32 47 44 32 32 The guide memberand the developer collecting screwconstitute a developer collecting portionserving as a collecting portion that collects the developer peeled off from the peeling sleeveof the peeling roller. In the developer collecting portion, the developer collecting screwis positioned lower than the rotation center of the peeling rollerin the vertical direction, and conveys the developer delivered, i.e., collected, from the peeling rollerwhile stirring the developer.

45 32 45 45 32 40 31 45 32 44 45 45 44 45 44 32 a a The guide memberserving as a guide portion is disposed below the rotation center of the peeling rollerin the vertical direction, and arranged such that a position on the guide memberwhere the guide memberand the peeling rollerare closest, i.e., closest position C, is higher than a center of the rotation shaft, i.e., rotation center, of the second developing rollerin the vertical direction. The guide memberguides the developer peeled off by the peeling rollertoward the developer collecting screw. Such a guide memberhas an inclined surfaceon which the developer slides down by its own weight in order to more reliably guide the peeled developer toward the developer collecting screw. The inclined surfaceis inclined with respect to a horizontal direction such that a portion adjacent to the developer collecting screwis positioned lower than the position below the peeling roller.

44 46 44 45 The developer collecting screwserving as a collecting member and a conveyance portion conveys the collected developer to a developer circulating portiondescribed below. That is, the developer collecting screwis a screw conveyance member used to convey the developer sliding down the inclined surface of the guide memberand collected in one direction while stirring the developer.

46 30 46 50 42 43 46 30 42 43 47 46 46 47 The developer circulating portionis a supply portion for supplying the developer to the first developing roller, and the developer circulating portionincludes a regulating member, the developer supplying screw, and the developer stirring screw. In the developer circulating portion, the developer is supplied to the first developing rollerwhile being fed in the substantially horizontal direction and stirred by the developer supplying screwand the developer stirring screw. As described above, the developer collected by the developer collecting portionfalls by its own weight and is introduced into the developer circulating portion. That is, the developer circulating portionis positioned lower than the developer collecting portionwith respect to the vertical direction.

42 43 44 42 43 44 42 43 44 30 The developer supplying screw (a first conveyance portion), the developer stirring screw (a third conveyance portion), and the developer collecting screw (a second conveyance portion)are screw conveyance members that convey the developer in one direction while stirring the developer, and the developer supplying screwand the developer stirring screware positioned lower than the rotation center of the developer collecting screwin the vertical direction. In addition, the developer supplying screw, the developer stirring screw, and the developer collecting screware disposed such that rotation axes thereof are substantially parallel to each other. The rotation axis of each screw is substantially parallel to the rotation axis of the first developing roller.

42 30 43 48 70 42 43 48 70 42 43 48 71 42 72 43 The developer supplying screwis positioned between the first developing rollerand the developer stirring screw, and a partition wallof the developing containeris disposed between the developer supplying screwand the developer stirring screw. The partition wallof the developing containerextends in a rotation axis direction of the developer supplying screwand the developer stirring screw. The partition wallhas a communication port (not illustrated) for communication between a first conveyance path (a first chamber)through which the developer is fed by the developer supplying screwand a second conveyance path (a third chamber)through which the developer is fed by the developer stirring screw.

44 73 70 47 44 71 42 42 45 73 44 73 a The developer stirred by the developer collecting screwpasses through a communication port (not illustrated) formed in a partition wallof the developing containerbetween a developer collecting chamber (a second chamber)in which the developer collecting screwis disposed and the first conveyance path (the first chamber)in which the developer supplying screwis disposed, and falls toward the developer supplying screwby its own weight. The guide memberdescribed above is formed integrally with the partition wall, and the developer collecting screwis disposed above the partition wall.

44 46 30 42 71 42 A position of the communication port through which the developer stirred by the developer collecting screwfalls by its own weight and is introduced into the developer circulating portionis preferably disposed to avoid a region where the developer is supplied toward the first developing roller, i.e., an intermediate portion of the developer supplying screwin the rotation axis direction. In the present embodiment, it is assumed that the position of the communication port is a position within a range of a downstream end portion, i.e., terminal end portion, of the first conveyance path, in which the developer supplying screwis disposed, in a developer conveyance direction.

42 43 71 42 72 43 48 42 43 70 30 2 FIG. The developer conveyance directions of the developer supplying screwand the developer stirring screware opposite to each other. A start end side, i.e., an upstream end side in the developer conveyance direction, and a terminal end side, i.e., a downstream end side in the developer conveyance direction, of the first conveyance pathin which the developer supplying screwis disposed communicate with a terminal end side and a start end side of the second conveyance pathin which the developer stirring screwis disposed via the communication port provided in the partition wall. Therefore, the developer circulates in a rotational direction of the developer supplying screwand the developer stirring screwindicated by arrows inand in the substantially horizontal direction inside the developing container, and a part of the developer is supplied toward the first developing roller.

51 43 70 27 51 27 72 43 2 FIG. 1 FIG. A developer replenishment port(refer to) is provided above the developer stirring screwin the developing container, and is connected to the developer storageY (refer to). The developer replenishment portis configured to be able to replenish the developer contained in a bottle loaded in the developer storageY to the second conveyance pathin which the developer stirring screwis disposed.

27 1 1 43 As described above, since the weight ratio of the toner of the developer contained in the bottle of the developer storageY is higher than the weight ratio of the toner of the developer in the developing apparatusY, the weight ratio of the toner of the developer in the developing apparatuscan be maintained constant by adjusting the developer being replenished to the developer stirring screw.

49 46 49 1 27 27 2 FIG. A toner density detection sensor(refer to) is provided to detect a toner density in the developer contained in the developer circulating portion. The toner density detection sensoris a sensor that detects magnetic permeability of the developer. Since the toner density corresponds to the amount of toner consumption in the developing apparatusY, the toner density is used for controlling developer replenishment from the developer storageY. For example, when it is detected that the toner density is lower than a predetermined value, the developer is replenished from the developer storageY. Since the magnetic permeability of the developer changes depending on the toner density, the toner density can be detected using the magnetic permeability.

50 30 46 30 50 30 33 30 50 The regulating memberis disposed adjacent to the first developing roller, and is used to regulate the amount of developer supplied from the developer circulating portionto the first developing roller. For example, the regulating membercan be configured to regulate the amount of developer attracted to the first developing rollerbased on a gap between the surface of the first developing sleeveof the first developing rollerand an end portion of the regulating member.

70 46 30 30 31 30 31 32 31 32 38 32 47 46 In a developer circulation path in the developing container, the developer is fed in the substantially horizontal direction while being stirred in the developer circulating portion, is then supplied to the first developing roller, and is delivered from the first developing rollerto the second developing rollerpositioned higher than the first developing rollerbased on the magnetic force. Then, the developer is delivered again from the second developing rollerto the peeling rollerpositioned on the side surface of the second developing rollerbased on the magnetic force, is then peeled off from the peeling rollerby the peeling magnetwithin the peeling roller, is further collected by the developer collecting portion, and is introduced again into the developer circulating portion.

As described above, in the present embodiment, a two-component developing system is used as a developing system, and a mixture of a nonmagnetic toner having a negative charging polarity and a magnetic carrier is used as the developer. The nonmagnetic toner is charged negatively by frictional electrification with the magnetic carrier, and the magnetic carrier is charged positively. The nonmagnetic toner is obtained by incorporating a colorant and a wax component in a resin such as a polyester resin or a styrene acrylic resin, pulverizing or polymerizing the resin into powder, and adding fine powder of titanium oxide, silica, or the like to the surface. The magnetic carrier is obtained by applying resin coating to a surface layer of a core formed of ferrite particles or resin particles kneaded with magnetic powder. A toner density, i.e., weight ratio of the toner contained in the developer, in the developer in an initial state is 8% in the present embodiment.

2 2 2 Note that the magnetic carrier preferably has a magnetization amount per unit weight of 40 to 80 Am/kg or less in an applied magnetic field of 1000 oersted. When the magnetization amount of the magnetic carrier is reduced, there is an effect of suppressing scavenging by a magnetic brush, but adhesion of the magnetic carrier to the nonmagnetic sleeve by a magnetic field generating portion becomes difficult, and image defects such as adhesion of the magnetic carrier to the photosensitive drum may occur. When the magnetization amount of the magnetic carrier is larger than the above range, image defects may occur due to the pressure of the magnetic brush as described above. In the present embodiment, a magnetic carrier whose magnetization amount per unit weight is 63 Am/kg is used. The magnetization amount of the magnetic carrier was measured using a vibrating magnetic field-type automatic magnetic characteristic recording apparatus BHV-30 manufactured by RIKEN Denshi Co., Ltd. For a magnetic characteristic value of the magnetic carrier, an external magnetic field of 1000 oersted is created, and a strength of magnetization at that time is obtained. The magnetic carrier is packed in a cylindrical plastic container so as to be sufficiently dense. In this state, a magnetization moment is measured, the actual weight when a sample is put is measured, and the strength of magnetization (Am/kg) is obtained.

1330 3 A true specific gravity of the magnetic carrier is determined by a dry automatic density type AccuPycmanufactured by Shimadzu Corporation. In the present embodiment, a magnetic carrier having a true specific gravity, i.e., density, of 4.6 (g/cm) was used. In addition, a magnetic carrier having a weight average diameter of 35 μm (radius b=17.5 μm) was used.

In general, in the two-component development method using a toner and a carrier, both the toner and the carrier are charged to predetermined polarities by being brought into frictional contact with each other, and thus has a feature that stress received by the toner is less than that of a one-component developing system using a one-component developer. On the other hand, the long-term use increases soiling, i.e., spent, attached to the surface of the carrier, and thus an ability to charge the toner gradually decreases. As a result, issues such as fogging and toner scattering occur. In order to prolong the life of a two-component developing apparatus, it is conceivable to increase the amount of carriers contained in the developing apparatus, but such a configuration is not desirable, since the size of the developing apparatus may be increased.

27 1 1 1 1 In order to solve the above issue related to the two-component developer, an auto carrier refresh (ACR) method is adopted in the present embodiment. The ACR method is a method of suppressing an increase in deteriorated carrier by replenishing a new developer from the developer storageY into the developing apparatusY little by little and discharging the developer with deteriorated charging performance little by little from a discharge port (not illustrated) of the developing apparatusY. As a result, the deteriorated carrier in the developing apparatusY is gradually replaced with the new carrier, and the charging performance of the carrier in the developing apparatusY can be kept substantially constant.

1 71 42 33 33 33 36 33 33 33 50 28 33 In the developing apparatusY of the present embodiment configured as described above, the developer in the first conveyance pathis supplied via the developer supplying screwto the first developing sleeve, and a predetermined amount of developer supplied to the first developing sleeveis borne on the first developing sleeveby the magnetic field generated by the first developing magnet, and forms a developer accumulation. The two-component developer on the first developing sleevepasses through the developer accumulation by the rotation of the first developing sleeve, forms a thin layer coating on the surface of the first developing sleeveby the regulating member, and is carried to a development region facing the photosensitive drumY. In the development region, the developer on the first developing sleeveis napped and a magnetic brush is formed.

33 28 28 33 33 In a first development region where the first developing sleeveand the photosensitive drumY face each other, the electrostatic latent image formed on the photosensitive drumY is developed by developing bias applied to the first developing sleeve. In the present embodiment, the developing bias applied to the first developing sleevehas a waveform in which both an AC electric field and a DC electric field are applied, but alternatively, the developing bias may only have a DC electric field.

34 34 34 28 28 33 34 The two-component developer is used for a developing process in the first development region, and then delivered to the second developing sleeveat a position close to the second developing sleeve, thereafter fed to a second development region where the second developing sleeveand the photosensitive drumY face each other. In the second development region, a same developing bias as that applied in the first development region is applied, and toner that is insufficient with respect to the potential of the electrostatic latent image on the photosensitive drumY is supplemented and developed, and toner that has been developed excessively is collected to prepare a uniform toner image. A bias having different waveforms may be applied as the developing bias applied to the first developing sleeveand the developing bias applied to the second developing sleeve.

37 34 34 35 38 35 32 35 35 38 47 The developer having passed through the second development region is peeled off in a peeing magnetic field area formed by the second developing magnetincluded in the second developing sleeve. The developer peeled off from the second developing sleeveis attracted onto the surface of the peeling sleeveby the magnetic field formed by the peeling magnetincluded in the peeling sleeveof the peeling roller, and conveyed along the rotational direction of the peeling sleeve. Then, the developer is detached from the surface of the peeling sleeveby the peeing magnetic field formed by the peeling magnet, and is collected to the developer collecting portion.

36 37 38 30 31 32 3 4 5 FIGS.,, and Next, the magnetic pole configurations of the first developing magnet, the second developing magnet, and peeing magnetwithin the first developing roller, the second developing roller, and the peeling rollerillustrated inwill be described.

3 FIG. 4 5 FIGS.and 36 30 101 1 102 2 103 2 104 3 105 3 106 4 107 1 36 106 30 31 101 107 33 As illustrated in, the first developing magnetwithin the first developing rollerhas the plurality of magnetic poles(S),(N),(S),(N),(S),(N), and(N), wherein S and N indicate whether the magnetic pole is an S pole or an N pole, and the numerals are assigned for distinguishment from other magnetic poles. According to the present embodiment, the first developing magnetincludes a total of seven magnetic poles. The same applies to. Among the magnetic poles, the magnetic poleis a delivery pole for delivering the developer from the first developing rollerto the second developing roller. The magnetic polestoare arranged in number order in the rotational direction of the first developing sleeve.

106 33 34 37 31 106 107 42 33 101 102 103 104 105 107 33 106 33 34 33 201 37 31 The magnetic poleis a magnetic pole for delivering the developer from the first developing sleeveto the second developing sleeveby a magnetic field generated in cooperation with the second developing magnetof the second developing roller, and hereinafter, may be referred to as the delivery pole. The magnetic poleis an N pole, and is used to attract the developer supplied from the developer supplying screwonto the first developing sleeve. The magnetic poles,,,, andare an S pole, an N pole, an S pole, an N pole, and an S pole, respectively, and are used to feed the developer attracted by the magnetic poleupward as the first developing sleeverotates. The magnetic poleis an N pole, and delivers the developer from the first developing sleeveto the second developing sleevefacing the first developing sleeveby a magnetic field generated in cooperation with the magnetic polein the second developing magnetwithin the second developing rolleras described above.

110 106 106 107 106 33 106 110 33 34 110 210 37 310 38 4 FIG. 5 FIG. In the present embodiment, a low magnetic force portionhaving a magnetic force lower than that of the magnetic poleis formed by a repulsive magnetic field generated in cooperation between the magnetic poleand the magnetic poledisposed downstream of the magnetic polein the rotational direction of the first developing sleeveand having the same magnetic polarity as the magnetic pole. The low magnetic force portionpromotes delivery of the developer from the first developing sleeveto the second developing sleeve. Note that the low magnetic force portionhas almost no magnetic force in the present embodiment, but may have a low magnetic force, and for example, may be a magnetic pole having a magnetic force, i.e., absolute value of a normal component Br of the magnetic flux density, of 10 mT or less, or even 5 mT or less. The same applies to a low magnetic force portionof the second developing magnetillustrated inand a low magnetic force portionof the peeling magnetillustrated in.

4 FIG. 37 31 201 4 202 5 203 5 204 6 205 6 206 7 207 7 201 31 30 201 207 34 As illustrated in, the second developing magnetwithin the second developing rollerhas the plurality of magnetic poles(S),(N),(S),(N),(S),(N), and(S), a total of seven magnetic poles. The magnetic poleis a receiving pole for the second developing rollerto receive the developer from the first developing roller. The magnetic polestoare arranged in number order in the rotational direction of the second developing sleeve.

201 33 34 107 36 30 201 207 34 35 38 32 207 The magnetic poleis a magnetic pole for attracting the developer from the first developing sleeveto the second developing sleeveby a magnetic field generated in cooperation with the magnetic poleof the first developing magnetof the first developing roller, and hereinafter, may be referred to as the receiving pole. The magnetic poleis a magnetic pole for delivering the developer from the second developing sleeveto the peeling sleeveby a magnetic field generated in cooperation with the peeling magnetof the peeling roller, and hereinafter, may be referred to as the delivery pole.

201 106 30 33 34 202 203 204 205 206 201 34 207 203 28 203 34 35 34 303 38 32 Further, the receiving poleis an S pole having a magnetic polarity different from that of the magnetic pole, and is used to attract the developer from the first developing roller, i.e., first developing sleeve, onto the second developing sleeveas described above. The magnetic poles,,,, andare an N pole, an S pole, an N pole, an S pole, and an N pole, respectively, and are used to feed the developer attracted by the magnetic poleupward as the second developing sleeverotates. The magnetic poleserving as a delivery pole is an S pole, and delivers the developer having passed through a development region between the magnetic poleand the photosensitive drumY corresponding to the magnetic polefrom the second developing sleeveto the peeling sleevefacing the second developing sleeveby a magnetic field generated in cooperation with the magnetic poleof the peeling magnetwithin the peeling roller.

210 207 201 207 201 34 201 210 33 34 210 33 34 In the present embodiment, the low magnetic force portionhaving a magnetic force lower than that of the magnetic poleis formed by a repulsive magnetic field generated in cooperation between the magnetic poleand the magnetic poledisposed upstream of the magnetic polein the rotational direction of the second developing sleeveand having the same magnetic polarity as the magnetic pole. The low magnetic force portionpromotes delivery of the developer from the first developing sleeveto the second developing sleeve. In addition, the low magnetic force portioncan prevent the developer from being attracted to the closest portions of the first developing sleeveand the second developing sleeve, so that a pressure applied to the developer can be suppressed.

5 FIG. 38 32 301 8 302 8 303 9 304 9 305 10 301 305 35 As illustrated in, the peeling magnetwithin the peeling rollerhas the plurality of magnetic poles(N),(S),(N),(S), and(N), a total of five magnetic poles. The magnetic polestoare arranged in number order in the rotational direction of the peeling sleeve.

303 34 35 207 37 31 303 303 207 34 35 301 302 304 35 35 302 303 35 302 302 301 35 35 305 301 310 301 301 305 The magnetic poleserving as a receiving pole is a magnetic pole for attracting the developer from the second developing sleeveto the peeling sleeveby the magnetic field generated in cooperation with the magnetic poleof the second developing magnetof the second developing roller, and hereinafter, may be referred to as the receiving pole. The magnetic poleis an N pole that is of different polarity as the magnetic pole, and is used to attract the developer peeled off from the second developing sleeveto the peeling sleeveas described above. The magnetic poles,, andare an N pole, an S pole, and an S pole, respectively, and are used to feed the developer on the peeling sleeveas the peeling sleeverotates. In particular, the magnetic poleis used to feed the developer attracted by the magnetic poleupward as the peeling sleeverotates. Hereafter, the magnetic polemay be referred to as the feeding pole. The magnetic poleis an N pole, and is a peeling pole used to peel off the developer attracted to the peeling sleevefrom the peeling sleeveby a repulsive magnetic field generated in cooperation with the magnetic polehaving the same magnetic polarity, and hereafter, it may be referred to as the peeling pole. The low magnetic force portionhaving a magnetic force lower than that of the magnetic poleis formed between the magnetic poleand the magnetic pole.

60 31 32 31 32 60 1 60 62 61 69 6 FIG. 2 FIG. Next, a duct, which is a suction cleaning configuration for cleaning scattered toner generated at the second developing rollerand the peeling roller, will be described.is a cross-sectional view illustrating an arrangement of the second developing roller, the peeling roller, and the duct, i.e., scattered toner collecting duct,according to the present embodiment. The developing apparatusY is equipped with the ductincluding a first duct walland a second duct wall, and an air suction device(refer to).

62 70 30 31 32 62 32 47 62 62 32 62 62 35 32 62 62 35 32 62 62 62 62 60 b c b b c b a a The first duct wallcovers a part of an inner space of the developing containerin which the first developing roller, the second developing roller, and the peeling rollerare disposed and in which the developer is stored, and prevents scattering of the developer from the inner space to the exterior. In the present embodiment, the first duct wallcovers an upper area of the peeling rollerand the developer collecting portion. Specifically, the first duct wallincludes a first wall portionthat is positioned above a peak of the peeling rollerin the vertical direction, and a second wall portionthat is extended upstream of the first wall portionin the rotational direction of the peeling sleeve, and is positioned closer to the peeling rollerthan the first wall portion. That is, in the present embodiment, the first duct wallis disposed to extend upstream in the rotational direction of the peeling sleevefrom the position above the peeling roller, and is bent diagonally downward in midway. Further, the edge of the second wall portionopposite to the first wall portionis an edgeof the first duct wallon a suction portside.

62 70 61 62 32 61 70 70 61 31 28 31 61 31 62 62 60 61 62 31 a a As described, the first duct wallcovers an upper portion of a part of the inner space of the developing container, and the second duct wallis disposed on an outer side of the first duct wallwith respect to the rotation center of the peeling roller. In the present embodiment, the second duct wallconstitutes a part of an outer wall of the developing container, but it may be independent from the outer wall of the developing container. The second duct wallis extended above the second developing roller, the edge thereof facing the photosensitive drumY with a gap therebetween, and covers the upper portion of the second developing roller. Specifically, the second duct wallis extended toward the second developing rollerside, i.e., developing roller side, than the edgeof the first duct wallon the suction portside. In the present embodiment, the second duct wallis extended from above the first duct wallin the vertical direction to a position facing the second developing roller.

60 60 62 61 31 60 60 62 62 61 60 74 31 32 32 a a a a Further, the suction portof the ductconstituted of the first duct walland the second duct wallis provided above the second developing roller. Specifically, the suction portis an opening portion on a first end side of the ductformed between the edgeof the first duct walland a part of the second duct wall. The suction portis positioned downstream of an opposing portionat which the second developing rollerand the peeling rollerface each other with respect to the rotational direction of the peeling roller.

60 69 69 69 60 60 70 69 a On a second end side of the duct, the ducts of developing apparatuses for the respective colors are merged and connected to the air suction device. The air suction deviceis a fan, for example, and by driving the air suction device, the developer scattered inside the developer container during developing operation is sucked through the suction portvia the duct. Thereby, the developer scattered to the exterior from the inner side of the developing containermay be reduced. When executing the image forming operation, the air suction deviceis activated to perform suction of the developer being scattered. The suction operation is performed at all times during forming of image.

6 FIG. 62 32 62 35 60 32 62 32 47 60 32 62 32 62 a As illustrated in, the first duct wallis arranged along the peeling roller. That is, the first duct wallextends downstream of the peeling sleevein the rotational direction from the suction port, and is arranged to face a part of the peeling rollerwith a gap therebetween. Further, the first duct wallis extended further from the position facing the peeling rollerto cover the upper area of the developer collecting portion. Therefore, the suction passage of the ductis disposed on an opposite side of the peeling rollerinterposing the first duct wall. In the present embodiment, a closest distance A between the peeling rollerand the first duct wallis set to 1.5 mm.

60 62 62 32 60 60 32 74 31 32 60 c The closest distance A is preferably within a range of 0.5 mm or more and 20 mm or less from the viewpoint of carrier collection in the ductand retention of developer. In the present embodiment, the closest distance A between the second wall portionof the first duct walland the peeling rolleris preferably set to 0.5 mm or more and 20 mm or less. If the closest distance A is large, the carrier is easily collected by the duct, and the ductmay be clogged easily by the carrier. Further, if the closest distance A is small, the developer may be retained, and the developer may not be easily carried by the peeling roller. In such a case, reverse flow of the developer may occurs, and by the developer returning toward the opposing portion, the co-rotation of developer on the second developing rollermay occur, which may lead to image defects. Therefore, it is preferable to set the closest distance A between the peeling rollerand the ductto 0.5 mm or more and 20 mm or less.

7 FIG. 30 31 32 42 43 44 30 31 32 60 100 illustrates a configuration of a developing apparatus according to a conventional example disclosed in Japanese Patent Application Laid-Open Publication No. 2018-124338. According to the conventional example, similar to the present embodiment, the developing apparatus includes a first developing rollerA, a second developing rollerA, a peeling rollerA, a developer supplying screwA, a developer stirring screwA, and a developer collecting screwA. The first developing rollerA, the second developing rollerA, and the peeling rollerA are respectively rotated in an arrow direction. However, the conventional example is not provided with the ductfor sucking the developer as according to the present embodiment. Therefore, the developer scattered in the developing container may be scattered to the exterior of the developing container. Then, the inner side of the image forming apparatusmay be soiled by the developer, or the output image may be soiled.

60 60 1 33 30 34 31 35 32 30 31 32 60 31 32 60 6 FIG. Next, a relationship between suction of scattered toner by the ductand clogging of scattered carrier in the ductwill be described with reference to. In the present embodiment, as described above, the developer inside the developing apparatusY is moved from the surface of the first developing sleeveof the first developing rollerto the surface of the second developing sleeveof the second developing roller, and thereafter, transferred to the surface of the peeling sleeveof the peeling roller. The processing speed of the image forming apparatuses is increasing, and along therewith, the rotating speeds of the first developing roller, the second developing roller, and the peeling rollerare also increasing. Therefore, while the developer is carried on the respective sleeves, in a case where the napping of the magnetic brush is collapsed between magnetic poles, the toner and the carrier may be easily detached from the sleeves and scattered. Therefore, in the present embodiment, as a countermeasure against toner scattering, the ductis disposed above the second developing rollerand the peeling roller, as described above. Then, the scattered toner is collected by the duct.

34 35 35 35 60 60 60 60 Further, airflow occurs by the second developing sleeveand the peeling sleevethat are rotated at high speed as described above, and the carrier that has been detached by centrifugal force may be scattered by the airflow. The airflow flows along the rotational direction of the respective sleeves, and the airflow near the peeling sleeveflows along the rotational direction of the peeling sleeve. The scattered carrier moves along with the airflow and is sucked into the duct. The carrier sucked into the ductcauses clogging of the duct, and causes deterioration of collection efficiency of scattered toner. Therefore, it is necessary to suppress the carrier from being collected into the duct.

8 FIG. 8 FIG. 62 62 60 60 32 a a Example 1, which is one example of a configuration for suppressing scattering of carrier as described above in the configuration of the present embodiment will be described with reference to. In Example 1, a relationship between the position of the edgeof the first duct wall, which is the end portion of the ducton the suction portside, and the magnetic poles of the peeling magnet disposed inside the peeling rolleris defined as illustrated in.

8 FIG. 1 301 35 62 62 35 1 301 62 301 62 35 62 a a That is, in the present embodiment, as illustrated in, a peak position, i.e., pole position, P, which is a position of a maximum value of a normal component of a magnetic flux density of the peeling poleon the peeling sleeve, is positioned downstream of the edgeof the first duct wallon the suction port side in the rotational direction of the peeling sleeve. Further, the peak position Pof the peeling poleis positioned at a position facing the first duct wall. According to the present embodiment, the entirety of the peeling poleis positioned downstream of the edgein the rotational direction of the peeling sleeve, and faces the first duct wall.

1 301 62 62 35 35 32 60 35 32 60 60 a a As described, by positioning the peak position Pof the peeling poledownstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve, the developer carried on the peeling sleeveis peeled off from the peeling rollerdownstream of the suction portin the rotational direction of the peeling sleeve. Therefore, the developer peeled off from the peeling rollerwill not be sucked easily into the duct, and the carrier scattered by the peeling off of the developer may be suppressed from being collected into the duct.

302 301 303 301 35 2 62 2 302 35 62 62 35 a a According to the present embodiment, the feeding pole, which is a magnetic pole adjacent to the peeling poledownstream of the receiving poleand upstream of the peeling polewith respect to the rotational direction of the peeling sleeve, also has a peak position Ppositioned downstream of the edge. That is, the peak position, i.e., pole position, P, which is a position of a maximum value of a normal component of a magnetic flux density of the feeding poleon the peeling sleeve, is positioned downstream of the edgeof the first duct wallon the suction port side in the rotational direction of the peeling sleeve.

302 32 301 302 60 60 2 302 62 62 60 a The feeding polecauses less scattering of carrier from the peeling rollercompared to the peeling pole, but scattering of carrier occurs at a napping collapse position which is positioned downstream of the feeding pole, and if the scattered carrier is caught in the airflow of the duct, the carrier will be collected into the duct. Therefore, according to the present embodiment, the peak position Pof the feeding poleis positioned downstream of the edgeof the first duct wall, such that the collecting of carrier by the ductcan be suppressed more efficiently.

9 FIG. 8 FIG. 38 1 301 1 301 62 62 35 a illustrates a configuration of a Comparative Example 1. In Comparative Example 1, the peeling magnetis rotated upstream in the rotational direction with respect to the configuration of Example 1 illustrated in, and the position of the peak position Pof the peeling poleis displaced from that of Example 1. That is, in the configuration of the Comparative Example 1, the peak position Pof the peeling poleis positioned upstream of the edgeof the first duct wallon the suction port side in the rotational direction of the peeling sleeve.

35 32 60 35 32 60 60 60 60 a In Comparative Example 1, the developer borne on the peeling sleeveis peeled off from the peeling rollerupstream of the suction portin the rotational direction of the peeling sleeve. Therefore, the developer peeled off from the peeling rolleris easily sucked into the duct, and the carrier scattered by the peeling of the developer is easily collected into the duct. Therefore, clogging of carrier in the ductmay easily occur, and when clogging of carrier occurs, the ability of the ductto suck in scattered toner is deteriorated, and the scattering of toner may not be suppressed sufficiently.

9 FIG. 1 301 62 62 38 1 301 62 62 62 62 a a a In the Comparative Example 1 illustrated in, the peak position Pof the peeling poleis positioned upstream of the edgeof the first duct wallby rotating the peeling magnet, but the same applies to a configuration in which the peak position Pof the peeling poleis positioned upstream of the edgeof the first duct wallby changing the position of the edgeof the first duct wall.

8 FIG. 1 301 62 62 32 1 301 1 301 35 32 1 301 32 32 32 a Returning to, the configuration of Example 1 will be described. As described above, the peak position Pof the peeling poleis positioned downstream of the edgeof the first duct wall, whereas from the viewpoint of peeling property of the developer from the peeling roller, the peak position Pof the peeling poleis preferably set as described below. That is, it is preferable that the peak position Pof the peeling poleis positioned downstream, in the rotational direction of the peeling sleeve, of the peak of the peeling rollerin the vertical direction. Further, the peak position Pof the peeling poleis preferably positioned higher than a rotation center R of the peeling rollerin the vertical direction. According to this configuration, the peeling performance of the developer from the peeling rolleris enhanced, such that the image defects caused by the developer being co-rotated with the peeling rollermay be suppressed.

1 301 60 1 32 35 31 35 60 1 8 FIG. 9 FIG. 8 FIG. 8 9 FIGS.and A relationship between the peak position Pof the peeling poleand correcting of carrier by the ductaccording to the configurations of Example 1 ofand Comparative Example 1 ofis shown in Table 1. In Table 1, an angle of the peak position Pis expressed by setting, among the points at which a horizontal line H () that passes the rotation center R of the peeling rollerintersect the surface of the peeling sleeve, the point on the second developing rollerside as 0 degrees, and defining the clockwise direction of, that is, the same direction as the rotational direction of the peeling sleeve, as positive. Further, in Table 1, in addition to Comparative Example 1 and Example 1, results having examined the collection of carrier by the ductin cases where the peak position Pis arranged at a plurality of angular positions are shown.

TABLE 1 PEAK POSITION P1 (°) 20 30 50 90 95 180 270 COLLECTION X ◯ ◯ ⊚ ⊚ ⊚ ◯ OF CARRIER NOTE COMPARATIVE EDGE PEAK OF EXAMPLE 1 HEIGHT OF LOWER THAN EXAMPLE 1 62a PEELING ROTATION ROTATION ROLLER 32 CENTER R CENTER R *⊚: VERY GOOD: Carrier collection by duct 60 was sufficiently suppressed ◯: GOOD: Carrier collection by duct 60 was suppressed to a level not causing carrier clogging X: POOR: Carrier was collected by duct 60 and carrier clogging occurred

60 60 60 1 1 62 1 1 32 1 31 1 1 1 a In Table 1, “very good” indicates that collection of carrier by the ductwas sufficiently suppressed. “Good” indicates that collection of carrier by the ductwas suppressed to a level not causing clogging of carrier. “Poor” indicates that carrier was collected by the ductand that clogging of carrier has occurred. Further, the case where the angle of the peak position Pis 20° is the Comparative Example 1, and in a case where the angle is 30°, the peak position Pis at a position facing the edge. Further, in a case where the angle of the peak position Pis 90°, the peak position Pis at a peak of the peeling rollerin the vertical direction, and a case where the angle is 95° is Example 1. Further, in a case where the angle is 180°, the peak position Pis on the opposite side from the second developing rollerand at a same height as the rotation center R in the vertical direction, whereas in a case where the angle is 270°, the peak position Pis arranged lower than the rotation center R in the vertical direction. It can be recognized based on Table 1 that it is preferable to set the peak position Pto 30° or more and 270° or less, and it is more preferable to set the peak position Pto 90° or more and 180° or less.

62 62 60 62 62 35 32 62 62 32 60 a a a Further, the position of the edgeof the first duct wallis preferably set as follows from the viewpoint of suppressing the collection of carrier into the duct. That is, the edgeof the first duct wallis preferably positioned upstream, in the rotational direction of the peeling sleeve, of the peak of the peeling rollerin the vertical direction. Further, the edgeof the first duct wallis preferably positioned higher than the rotation center R of the peeling rollerin the vertical direction. According to this configuration, the collection of carrier to the ductcan be suppressed further.

62 62 62 32 35 31 35 60 62 a a a 8 FIG. 8 FIG. The relationship between the position of the edgeof the first duct walland the collection of carrier according to the configuration of Example 1 is shown in Table 2. In Table 2, similar to the case shown in Table 1, an angle of the position of the edgeis expressed by setting, among the points at which a horizontal line H () that passes the rotation center R of the peeling rollerintersect the surface of the peeling sleeve, the point on the second developing rollerside as 0 degrees, and defining the clockwise direction of, that is, the same direction as the rotational direction of the peeling sleeve, as positive. Further, in Table 2, results having examined the collection of carrier by the ductin cases where the edgeis arranged at a plurality of angular positions are shown.

TABLE 2 EDGE 62a POSITION OF FIRST DUCT WALL 62 (°) −20 0 50 90 95 COLLECTION ◯ ⊚ ⊚ ⊚ ◯ OF CARRIER NOTE HEIGHT OF PEAK OF PEAK ROTATION PEELING POSITION CENTER R ROLLER 32 P1 * ⊚: VERY GOOD: Carrier collection by duct 60 was sufficiently suppressed ◯: GOOD: Carrier collection by duct 60 was suppressed to a level not causing carrier clogging

62 62 62 a a In Table 2, “very good” and “good” indicate the same states as described in Table 1. It can be recognized from Table 2 that it is preferable to set the position of the edgeof the first duct wallto −20° or more and 95° or less, and even more preferable to set the position of the edgeto 0° or more and 90° or less.

1 301 62 62 35 60 2 302 62 60 60 a a In the case of Example 1, by positioning the peak position Pof the peeling poledownstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve, it is possible to suppress the scattered carrier from being collected into the duct. Further, in Example 1, the peak position Pthe feeding poleis also positioned downstream of the edge. Therefore, the collection of carrier by the ductmay be suppressed even more efficiently. As a result, the deterioration of suction ability of scattered toner by the ductmay be suppressed, and the scattering of toner can be suppressed for a long time.

10 FIG. 8 FIG. 38 1 301 2 302 1 301 62 62 35 2 302 62 62 35 a a Example 2, which is one example of a configuration for suppressing scattering of carrier in the configuration of the present embodiment, will be described with reference to. In Example 2, the peeling magnetis rotated upstream in the rotation direction from the configuration of Example 1 illustrated in, such that the positions of the peak position Pof the peeling poleand the peak position Pof the feeding poleare displaced with respect to Example 1. That is, in Example 2, similar to Example 1, the peak position Pof the peeling poleis positioned downstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve. However, in Example 2, unlike Example 1, the peak position Pof the feeding poleis positioned upstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve.

2 302 62 62 35 60 1 301 62 62 35 2 302 62 60 a a a As according to Example 1, if the peak position Pof the feeding poleis positioned downstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve, the collection of carrier by the ductmay be suppressed further. However, as according to Example 2, if the peak position Pof the peeling poleis positioned downstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve, even if the peak position Pof the feeding poleis positioned upstream of the edge, the collection of carrier by the ductcan be suppressed, though the effect thereof is lower than that of Example 1.

2 302 60 2 302 32 35 31 35 60 2 62 8 FIG. 10 FIG. 8 FIG. 8 FIG. a The relationship between the peak position Pof the feeding poleand the collection of carrier into the ductaccording to the configuration of Example 1 ofand Example 2 ofis shown in Table 3 In Table 3, similar to the case shown in Table 1, an angle of the peak position Pof the feeding poleis expressed by setting, among the points at which a horizontal line H () that passes the rotation center R of the peeling rollerintersect the surface of the peeling sleeve, the point on the second developing rollerside as 0 degrees, and defining the clockwise direction of, that is, the same direction as the rotational direction of the peeling sleeve, as positive. Further, in Table 3, in addition to Examples 1 and 2, a result having examined the collection of carrier into the ductin a case where the peak position Pfaces the edge(30°) is shown

TABLE 3 PEAK POSITION P2 (°) 20 30 35 COLLECTION ◯ ⊚ ⊚ OF CARRIER NOTE EXAMPLE 2 EDGE 62a EXAMPLE 1 * ⊚: VERY GOOD: Carrier collection by duct 60 was sufficiently suppressed ◯: GOOD: Carrier collection by duct 60 was suppressed to a level not causing carrier clogging

2 302 2 62 2 62 a a. In Table 3, “very good” and “good” indicate the same states as described in Table 1. It can be recognized from Table 3 that it is preferable to set the peak position Pof the feeding poleto 20° or more, and that it is possible to sufficiently suppress the collection of carrier even if the peak position Pfaces the edge. Further, it is recognized that it is more preferable to arrange the peak position Pdownstream of the edge

31 32 62 2 302 62 60 1 301 62 a a. Such an Example 2 is effective in a case where there is a limitation in the positional relationship of the second developing roller, the peeling roller, and the first duct wall, and it is difficult to position the peak position Pof the feeding poledownstream of the edge. Even if there is such a limitation, the collection of carrier by the ductmay be suppressed by positioning the peak position Pof the peeling poledownstream of the edge

11 FIG. 62 62 a In the configuration of the present embodiment, Examples 3 and 4, which are examples of the configuration for suppressing the scattering of toner, will be described with reference to. In Examples 3 and 4, confirmation was performed from the viewpoint of Fθ, which is a magnetic force applied on the carrier at the position of the edgeof the first duct wall.

38 35 Br: Magnetic flux density in a normal direction, i.e., vertical direction, with respect to an outer peripheral surface, i.e., upper surface, of the peeling sleeveat a certain point 35 Bθ: Magnetic flux density in a tangential direction with respect to the outer peripheral surface of the peeling sleeveat a certain point 35 35 Fr: Magnetic force applied in the normal direction with respect to the outer peripheral surface of the peeling sleeveat a certain point, wherein an attraction direction, i.e., direction toward the peeling sleeve, is referred to as negative 35 35 Fθ: Magnetic force applied in the tangential direction with respect to the outer peripheral surface of the peeling sleeveat a certain point, wherein the rotational direction of the peeling sleeveis referred to as positive A magnetic flux density and a magnetic force that the peeling magnetcreates will be described below. In the description of the present embodiment, Br, Bθ, Fr, and Fθ are defined as follows.

35 Unless denoted otherwise, Br, Bθ, Fr, and Fθ refer to the magnetic flux density or the magnetic force at a certain point on the peeling sleeve.

0 Next, a method for measuring a magnetic force according to the present embodiment will be described. The magnetic force according to the present embodiment can be calculated by a calculation method described below. The magnetic force acting on the carrier can be obtained by the following Expression (1). In the Expression, μrepresents the magnetic permeability of vacuum, u represents the magnetic permeability of the carrier, b represents the radius of the carrier, and B represents the magnetic flux density.

Based on Expression (2), Fr and Fθ can be calculated by acquiring Br and Bθ. The magnetic flux density Br was measured using a magnetic field measuring instrument “MS-9902” (Product Name) manufactured by F. W. BELL as the measuring instrument and setting the distance between a probe, which is a member of the measuring instrument, and the upper surface of the developing sleeve to approximately 100 μm.

z Further, Bθ may be obtained by the following method. A vector potential A(R, θ) at a measurement position of the magnetic flux density Br can be obtained using the measured magnetic flux density Br by the following expression.

z z A(r,θ) is obtained by setting the boundary condition to A(R, θ) and solving the following expression,

Then, Br and Bθ are obtained by the following expressions.

Fr and Fθ may be obtained by applying Br and Bθ measured and computed as described above to Expression (1). Further, based on the above Expression, the Fr distribution that is required according to the present embodiment may be obtained.

35 35 35 35 62 62 35 62 62 62 62 a a a −8 −8 11 FIG. In Example 3, when setting the magnetic force applied on the peeling sleevein the tangential direction is set to Fθ, the force of Fθ applied in the same direction as the rotational direction of the peeling sleeveas positive, and the force of Fθ applied in the opposite direction as the rotational direction of the peeling sleeveas negative, the Fθ on the peeling sleevecorresponding to the edgeof the first duct wallis set to +1.5×10N. Meanwhile, in Example 4, the Fθ on the peeling sleevecorresponding to the edgeof the first duct wallis set to −1.5×10N.illustrates a graph of the distribution of Fθ in the vicinity of the position of the edgeof the first duct wallaccording to Examples 1, 3, and 4.

35 62 38 35 62 38 35 62 60 a a a In Example 1, the Fθ on the peeling sleevecorresponding to the position of the edgeis approximately 0, and extremely small. In Example 3, a peeling magnetwas used in which the Fθ on the peeling sleevecorresponding to the position of the edgeis greater than that of Example 1. In Example 4, a peeling magnetwas used in which the Fe on the peeling sleevecorresponding to the position of the edgeis smaller than that of Example 1. The collection of carrier into the ductwas confirmed for each of the Examples.

35 62 35 62 32 32 60 a a In Example 3, the Fe on the peeling sleevecorresponding to the position of the edgeis set large, such that the speed in which the developer moves on the peeling sleevecorresponding to the position of the edgebecomes faster than the rotating speed of the peeling roller. Therefore, the centrifugal force acting on the carrier is large, and the carrier is easily released from the peeling roller. Therefore, compared to Example 1, the carrier is easily collected into the duct.

35 62 35 62 32 32 32 32 32 62 32 62 32 74 31 a a Meanwhile, in Example 4, the Fθ on the peeling sleevecorresponding to the position of the edgeis set small, such that the speed in which the developer moves on the peeling sleevecorresponding to the position of the edgebecomes slower than the rotating speed of the peeling roller. Therefore, the centrifugal force acting on the carrier is small, and the carrier is not easily released from the peeling roller. However, the moving speed of the developer is slow, such that the height of the developer on the peeling rollertends to become high. Therefore, in Example 4, the height of the developer on the peeling rollerexceeded the closest distance A between the peeling rollerand the first duct wall. Therefore, the developer was retained at the position of the closest distance A between the peeling rollerand the first duct wall, and the developer could not be conveyed appropriately by the peeling roller, such that reverse flow of the developer occurred. By having the developer return toward the opposing portion, co-rotation of the developer on the second developing rolleroccurred, and image defects tended to occur.

60 As described above, the configuration of Example 1 enabled to suppress the occurrence of retention of the developer at the closest distance A position, and to suppress the collection of the carrier to the ductthe most.

35 62 60 a −8 −8 −9 −8 −8 The relationship between the Fθ on the peeling sleevecorresponding to the position of the edgeand the retention of developer and collection of carrier by the ductcorresponding to the configurations of Examples 1, 3, and 4 is illustrated in Table 4. In Table 4, in addition to Examples 1, 3, and 4, cases where Fθ is −1.0×10N (−1.0E-08) and where Fθ is +1.0×10N (1.0E-08) are shown. The Fθ of Example 1 is +0.9×10N (0.9E-09), the Fθ of Example 3 is +1.5×10N (1.5E-08), and the Fθ of Example 4 is −1.5×10N (−1.5E-08).

TABLE 4 Fθ (N) −1.5E−08 −1.0E−08 0.9E−09 1.0E−08 1.5E−08 COLLECTION ⊚ ⊚ ⊚ ⊚ ◯ OF CARRIER RETENTION OF ◯ ⊚ ⊚ ⊚ ⊚ DEVELOPER NOTE EXAMPLE 4 EXAMPLE 1 EXAMPLE 3 *COLLECTION OF CARRIER ⊚: VERY GOOD: Carrier collection by duct 60 was sufficiently suppressed ◯: GOOD: Carrier collection by duct 60 was suppressed to a level not causing carrier clogging *RETENTION OF DEVELOPER ⊚: VERY GOOD: No retention of developer occurred at position of closest distance A ◯: GOOD: Some retention of developer occurred at position of closest distance A, but image defect that occurred along therewith was within permissible range

In Table 4, “very good” and “good” in the “collection of carrier” column indicates the same states as described in Table 1. Further, “very good” in the “retention of developer” column indicates that no retention of developer occurred at the position of the closest distance A. “Good” refers to a state where some retention of developer occurred at the position of the closest distance A, but the image defect that occurred along therewith was within a permissible range.

35 62 60 35 62 60 35 62 a a a −8 −8 −8 −8 Based on Table 4, it was recognized that from the viewpoint of suppressing retention of developer at the position of the closest distance A, it is preferable to set the Fθ on the peeling sleevecorresponding to the position of the edgeof the first duct wall to +1.5×10N or less. Further, from the viewpoint of suppressing the collection of carrier by the duct, it is preferable to set the Fθ on the peeling sleevecorresponding to the edgeof the first duct wall to −1.5×10N or more. Further, from the viewpoint of both the suppression of retention of developer and the suppression of collection of carrier by the duct, it is preferable to set the Fθ on the peeling sleevecorresponding to the edgeof the first duct wall to −1.0×10N or more and +1.0×10N or less.

35 62 60 35 62 60 60 a a In Example 3, the Fθ on the peeling sleevecorresponding to the position of the edgeis set greater than Example 1, such that the retention of developer at the position of the closest distance A may be suppressed compared to Example 1. However, Example 1 enables to suppress the retention of developer and the collection of carrier by the ductcompared to Example 3. In Example 4, the Fθ on the peeling sleevecorresponding to the position of the edgeis set smaller than that of Example 1, such that the carrier is not easily scattered, and the retention of developer and collection of carrier by the ductmay be suppressed similarly as Example 1 or may be suppressed even more than Example 1. However, Example 1 enables to suppress the retention of developer at the position of the closest distance A compared to Example 4. Therefore, from the viewpoint of both the suppression of retention of developer and the suppression of collection of carrier by the duct, Example 1 is most preferable.

12 13 FIGS.and 12 FIG. 45 44 35 45 45 32 38 32 b In the configuration of the present embodiment, Example 5, which is an example of the configuration for suppressing the scattering of carrier, will be described with reference to. In Example 5, the position of the guide memberguiding the developer to the developer collecting screwwas changed with respect to the configuration of Example 1. That is, in Example 5, in a state where the normal component of magnetic flux density on the peeling sleeveis referred to as Br, as illustrated in, an edgeof the guide memberon the peeling rollerside faces a region where the absolute value of Br is 10 mT or less, preferably 5 mT or less. The configuration of the peeling magnetwithin the peeling rolleris the same as that of Example 1.

12 FIG. 45 45 310 38 310 35 45 45 310 32 44 32 b b As illustrated in, the edgeof the guide memberis arranged in proximity to a position facing the low magnetic force portionof the peeling magnet. Since the low magnetic force portionis a region in which the developer is peeled off from the peeling sleeve, by arranging the edgeof the guide memberat a position facing the low magnetic force portionas according to Example 4, the peeling property of the developer from the peeling rollermay be improved and the conveyance performance of the developer to the developer collecting screwmay be improved compared to the configuration of Example 1. As a result, the co-rotation of the developer on the peeling rollermay be suppressed, and the image quality of the output image can be improved.

13 FIG. 38 32 45 45 32 b is a graph illustrating the distribution of Br at the positions of the respective magnetic poles of the magnetic field generated by the peeling magnetinside the peeling roller. By disposing the edgeof the guide memberin a region where the absolute value |Br| of Br is 10 mT or less, the peeling performance of the developer from the peeling rollercan be enhanced.

45 45 32 45 45 32 35 31 35 32 45 45 b b b 8 FIG. 8 FIG. The relationship between the position of the edgeof the guide memberand peelability of the developer from the peeling rolleraccording to the configurations of Examples 1 and 5 is shown in Table 5. In Table 5, similar to the case shown in Table 1, an angle of the position of the edgeof the guide memberis expressed by setting, among the points at which the horizontal line H () that passes the rotation center R of the peeling rollerintersect the surface of the peeling sleeve, the point on the second developing rollerside as 0 degrees, and defining the clockwise direction of, that is, the same direction as the rotational direction of the peeling sleeve, as positive. Further, in Table 5, in addition to Examples 1 and 5, the results having examined the peelability of developer from the peeling rollerin a case where the position of the edgeof the guide memberis set to positions other than those of Examples 1 and 5 are shown.

TABLE 5 EDGE 45b POSITION OF GUIDE MEMBER 45 (°) 100 110 190 200 280 PEELABILITY Δ ⊚ ⊚ ⊚ ◯ NOTE EXAMPLE 5 EXAMPLE 1 *⊚: VERY GOOD: Peelability of developer from peeling roller 32 was satisfactory ◯: GOOD: Peelability of developer from peeling roller 32 was somewhat deteriorated but within a level not influencing output image Δ: AVERAGE: Peelability of developer from peeling roller 32 was deteriorated and output image was somewhat influenced

32 32 32 In Table 5, “very good” indicates that the peelability of developer from the peeling rollerwas satisfactory. “Good” indicates that the peelability of developer from the peeling rollerwas somewhat deteriorated but within a level not influencing the output image. “Average” indicates that the peelability of developer from the peeling rollerwas deteriorated and the output image was somewhat influenced.

45 45 45 45 b b It was recognized based on Table 5 that it is preferable to set the position of the edgeof the guide memberto 110° or more and 280° or less. Further, it was recognized that it is more preferable to set the position of the edgeof the guide memberwithin the range of 110° or more and 200° or less.

45 45 32 32 b In Example 5, sine the edgeof the guide memberon the peeling roller side faces the region in which the absolute value of Br is 10 mT or less, compared to the configuration of Example 1, the peelability of the developer from the peeling rollermay be improved. As a result, the co-rotation of developer on the peeling rolleris suppressed, and the image quality of the output image can be improved.

9 FIG. 7 FIG. 1 FIG. 60 32 60 1 301 62 62 35 a The following experiment was performed to confirm the effects of the respective configurations of Examples 1 to 5, Comparative Example 1 (), and the conventional example (). The developing apparatuses of the respective configurations were attached to the image forming apparatus illustrated in, and image formation was performed to 5000 sheets. In the respective configurations, the scattering of toner within the developing apparatus, the collection of carrier into the duct, the retention of developer at the position of the closest distance A, and the peelability of developer from the peeling rollerwere confirmed and evaluated. As for the conventional example, the ductis not provided, such that items other than scattering of toner were not evaluated. As for Comparative Example 1, the peak position Pof the peeling poleis disposed upstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve, such that the retention of developer was not evaluated. The results of the experiment are shown in Table 6.

TABLE 6 COLLECTION RETENTION PEELABILITY TONER OF CARRIER OF OF SCATTERING INTO DUCT DEVELOPER DEVELOPER CONVENTIONAL X — — — EXAMPLE COMPARATIVE ◯ X — X EXAMPLE 1 EXAMPLE 1 ◯ ⊚ ⊚ ◯ EXAMPLE 2 ◯ ◯ ⊚ ◯ EXAMPLE 3 ◯ ◯ ⊚ ◯ EXAMPLE 4 ◯ ⊚ ◯ ◯ EXAMPLE 5 ◯ ⊚ ⊚ ⊚ *TONER SCATTERING ◯: GOOD: Toner scattering in developing apparatus was sufficiently suppressed X: POOR: Toner scattering has occurred in developing apparatus *Collection of carrier into duct ⊚: VERY GOOD: Carrier collection by duct 60 was sufficiently suppressed ◯: GOOD: Carrier collection by duct 60 was suppressed to a level not causing carrier clogging X: POOR: Carrier was collected by duct 60 and carrier clogging occurred *Retention of developer ⊚: VERY GOOD: No retention of developer occurred at position of closest distance A ◯: GOOD: Some retention of developer occurred at position of closest distance A, but image defect that occurred along therewith was within permissible range *Peelability of developer ⊚: VERY GOOD: Peelability of developer from peeling roller 32 was satisfactory ◯: GOOD: Peelability of developer from peeling roller 32 was somewhat deteriorated but within a level not influencing output image Δ: AVERAGE: Peelability of developer from peeling roller 32 was deteriorated and output image was somewhat influenced

32 In Table 6, “good” in “toner scattering” indicates that the toner scattering in the developing apparatus was sufficiently suppressed. “Poor” indicates that toner scattering has occurred in the developing apparatus. Further, “very good”, “good”, and “poor” in the “collection of carrier into duct” column indicate the same states as described in Table 1. “Very good” and “good” in the “retention of developer” column indicate the same states as described in Table 4. “Very good” and “good” in the “peelability of developer” column indicate the same states as described in Table 5. “Poor” in the “peelability of developer” indicates that the peelability of the developer from the peeling rolleris deteriorated and the output image has been influenced.

60 1 301 62 62 35 a As can be seen from Table 6, the Comparative Example 1 and Examples 1 to 5, other than the conventional example, include the duct, such the toner scattering within the developing apparatus was sufficiently suppressed. Further, according to Comparative Example 1, the peak position Pof the peeling polewas disposed upstream of the edgeof the first duct wallin the rotational direction of the peeling sleeve, such that compared to Examples 1 to 5, the evaluation regarding collection of carrier into duct and peelability of developer were not good. As for the collection of carrier into duct, among Examples 1 to 5, the evaluations of Examples 1, 4, and 5 were high. As for the retention of developer, among Examples 1 to 5, the evaluations of Examples other than Example 4 were high. Even further, as for the peelability of developer, Examples 1 to 4 were okay, but the evaluation of Example 5 was high.

The respective embodiments were described based on a developing apparatus including two developing rollers, but the present disclosure is also applicable to a configuration having only one developing roller. That is, the present disclosure is applicable to a configuration in which there is one developing roller for developing the electrostatic latent image on an image developing member, such as a photosensitive drum, and in which a peeling roller for peeling the developer from the developing roller is provided.

100 42 43 44 The present invention is not limited to the configuration of each embodiment described above. For example, the image forming apparatusis not limited to the MFP, and may be a copier, a printer, or a facsimile machine. Further, the configurations of the developer supplying screw, the developer stirring screw, and the developer collecting screware not particularly limited as long as the developer can be fed, and for example, a spiral blade or a paddle blade can be applied.

According to the present disclosure, collection of carrier by the duct may be suppressed.

While the present disclosure has been described with reference to embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2024-184367, filed Oct. 18, 2024 which is hereby incorporated by reference herein in its entirety.